This paper is part of a broader ongoing effort to elucidate signal processing as musical communication.1 In it, I draw an aesthetic distinction between three species of lateral dynamics processing which regularly recur in modern experimental hip hop, specifically, side-chain pumping, ducking and envelope following. I explain how these techniques relate on a procedural level, even as they serve different musical functions; and, finally, I consider why so little is written about these techniques in current research on popular music recording practice.

To be clear, I do not suggest that the techniques I examine below are revolutionary, nor that they are unknown by recordists working in genres other than hip hop. In fact, my point is precisely the opposite: the techniques I survey in this paper are as common as “tapping” and “power chords” once were in heavy metal. This makes their absence from academic research on popular music practice, including popular music recording practice, all the more conspicuous, in my opinion.2 It is precisely this absence the following study was designed to elucidate.

Side-Chain Pumping

The most obvious lateral dynamics processing technique in the hip hop lexicon is so-called “side-chain pumping.” To create this effect, recordists side-chain compressors set to process tracks with obvious sustain information to rhythmically active tracks like, most commonly, kick drum and snare. The volume of the side-chained track thus lowers and, then, pumps back to its original level each time the amplitude of the trigger registers above the threshold on the compressor, at a rate determined by its attack and release settings. This process creates the regularized rhythmic flexing known as “side-chain pumping.”

Figure 1. From top to bottom: (i) a synth pad side-chained to (ii) a kick drum playing straight quarter notes, and (iii) the resulting pad.

Example 1. Dabrye’s “Air” remixed by the author to emphasize side-chain pumping. Side-chaining commences at precisely 12 seconds into the track, after the first two iterations of the kick.

Hip hop recordists tend to use the side-chain on their compressors to buttress the groove, regularly transforming a pad, or ambience, into a rhythmic upstroke. Flying Lotus (FlyLo), for instance, makes regular and overt use of the side-chain on his compressors for this very purpose. A clear example of the celebrated producer’s extroverted approach to the side-chain can be heard on “Tea Leaf Dancers,” track one on his debut e.p. for Warp Records. Side-chained in its entirety, every component of “Tea Leaf Dancers”, including Andrea Triana’s lead vocal, pumps dramatically under the kick drum each time it sounds; and FlyLo does precisely the same on his remix of Madvillain’s “Shadows of Tomorrow (feat. Quasimoto)”. Lone, a well known British DJ, takes a similar approach on Ecstasy and Friends, side-chaining each track under the kick on all but one cut. Other celebrated champions of the side-chain include J-Dilla and Samiyam, and, to a lesser extent, Madlib, Dibiase, Prefuse 73 and Oh No.

Ducking

Though neither as common, nor immediately apparent, as side-chain pumping, ducking abounds in modern experimental hip hop. While ducking clearly resembles side-chain pumping in procedural terms, the techniques are aesthetically distinct. As noted, side-chain pumping alters the dynamic contour of tracks and, in the process, transforms pads and ambience into rhythmic upstrokes. Ducking, on the other hand, increases the textural density of tracks, and extends their temporal envelopes.3

To duck a signal, recordists can insert any number of tools into the signal chain. These include: (i) dedicated duckers; (ii) side-chained compressors with their makeup gain set for a substantial negative value; and (iii) noise gates with their ducking function engaged. The ducking mechanism is then laterally oriented such that it triggers based on the amplitude of whichever track recordists want to dynamically “duck under.”

One of the most common candidates for this treatment in hip hop are echoes and reverberations generated by lead vocal lines. Using whichever ducking mechanism they prefer, hip hop recordists routinely duck reverb and delay lines under the dry vocal tracks used to generate them. Ducked echoes and reverberations thus emerge at an unobtrusive volume whenever vocals are present, but pump to the dynamic fore the second they disappear.

Figure 2. From top to bottom: (i) a kick drum and (ii) its ducked delay line

The introduction to Danger Mouse’s “Lazer Beam”, track three on From Man To Mouse, provides an exceptionally clear illustration of this technique at work on a hip hop track. So, too, does Jay Da Flex’s dubstep remix of the Wu Tang Clan’s “Deep Space”, MF Doom’s lead vocal on Dabrye’s “Air”, and any cut from Mos Def’s most recent release, The Ecstatic. That said, it is FlyLo who once again makes most overt, and experimental, use of the device. The celebrated producer routinely invokes ducked echoes on lead vocal tracks, in conjunction with erratic stereo panning, to create the texturally dense — if not over-saturated — soundstage which characterizes his most recent vocal productions.

Envelope Following

Another common lateral dynamics processing technique in hip hop is envelope following, that is, the deliberate refashioning of one amplitude envelope to mimic — or, at the very least, to closely resemble — another. To achieve this, recordists use keyed gating. This entails laterally orienting a gate so it only stops attenuating signal when the amplitude of the key registers above its threshold.

A common candidate for envelope following in hip hop is the kick drum. Recordists insert a noise gate into the signal chain for a low frequency oscillator set to generate signal somewhere in the second or third octave, between roughly 40 and 90 Hertz. The gate is then keyed to the kick, and its threshold adjusted, such that the low frequency only sounds in unison with the kick, buttressing its every iteration with added bass components (albeit offset by the attack and hold settings on the keyed gate). Clear demonstrations of this “buttressing” technique can be heard throughout hip hop in general, but especially clearly on recent releases by FlyLo, Prefuse 73, J-Dilla, Samiyam and Hudson Mohawke.

Figure 3. From top to bottom: (i) a synth pad keyed to (ii) a kick drum playing straight quarter notes, and (iii) the resulting pad.

Example 3. Dabrye’s “Air” remixed by the author to include keyed gate buttressing kick drum with added bass components. Example 3 begins with the buttressing tone isolated for four measures. Once the track begins, however, buttressing only commences at 16 seconds into the track, after the first two iterations of the kick.

Summary & Recommendations

Though this paper is by no means exhaustive, the techniques I survey in it recur constantly in modern experimental hip hop productions. Side-chain pumping, ducking and envelope following are as foundational in experimental hip hop as “power chords” and “tapping” once were in heavy metal. Yet they remain conspicuously absent from the lion’s share of research on the genre; and, for that matter, they remain unnoticed in research on popular music recording practice at large.

Lacunae are to be expected in a field as young and diffuse as popular music studies. However, the present paucity of research on specific signal processing techniques signals the field’s institutional basis much more than its nascent state, in my opinion. Insightful and challenging studies of signal processing have indeed emerged in the last two decades, but these studies usually address the analytic priorities and concerns of disciplines that remain completely uninterested in musical technique per se, like cultural studies, sociology, media studies, cultural anthropology and political-economics.4 If it is mentioned at all in these studies, signal processing usually only registers as a site for social, cultural and industrial struggle; only a select few researchers offer much in the way of musical and technical details about the process.5 Not surprisingly, then, signal processing has failed to register as a fundamentally musical concern in the vast majority of published research on popular music practice.

Though one might reasonably expect technical manuals, trade journals and audio-engineering textbooks to “fill-in” the missing musical information I note, most do not address straightforwardly musical topics. Texts in this category usually only sketch the technical capacities of modern recording technologies, and provide a basic psychoacoustic rationale for a few core uses, or they rehearse broad procedural chronologies for certain historically significant recording sessions, without considering the larger aesthetic paradigms that recordists deployed their musical practice to service.6

Even as musicologists and music theorists turn their analytic attentions to pop records, they remain largely fixated on musical details that can be notated (ie., pitch relations, formal contour, metered rhythms, harmonic design, and so on). This is especially ironic given that so many analysts ostentatiously reject notation as an analytic tool now.7 No matter how avant-garde their methods, in other words, most musicologists and music theorists remain fixated on the very same musical details they have always analyzed. They simply disagree over how best to interpret those details now.8 Recording Practice itself, that is, musical practice of recording technology, continues to register in a very small, albeit growing, collection of articles and books.

The need for a research program designed to illuminate Recording Practice as musical practice is urgent. As Albin Zak (2001: 26) explains, “record making is a recent art form, and many of its artistic roles belong to no prior tradition…. we know what songwriters do, but what about sound engineers?” Scholars have tried to answer this very question using what seems like every disciplinary and interdisciplinary tool available, and yet Recording Practice in-and-of-itself remains stubbornly absent from the lion’s share of published research. In my opinion, it will remain absent until a unified “disciplinary” approach to analyzing record making (and not just records) finally emerges, an approach that conceives, and explains, musical practice of recording technology — say, tweaking the release time setting on a side-chained compressor or a keyed gate — as musical communication per se. Records present listeners with music; this much we know. Until analysts can connect that music to a concrete corpus of embodied procedures, though, Recording Practice itself is likely to remain the geeky “gearslut” of musical study — a crucial species of modern musical communications which analysts routinely devalue as nothing more than a technical support, something like scaffold-building, for the “true arts” of performance and composition.

About the Author

Jay Hodgson

University of Western Ontario

jhodgs5@uwo.ca

Notes

1 Other publications in this broader research project include: Hodgson 2010a and 2010b; and a forthcoming monograph from Wifrid Laurier Press, scheduled for publication early in 2012.

2 See the concluding section of this paper, headed “Summary & Recommendations,” for a more detailed description of this “conspicuous absence.”

3 Of course, this distinction is not terribly meaningful for a great many practicing recordists; side-chain pumping is a species of ducking, many argue, and nothing more on the matter needs to be said. Yet side-chain pumping and ducking are not merely aesthetically different. A crucial procedural difference between the two techniques can — and, from an analytic perspective, should — be made. As Alexander Case (2007: 183-184) explains: “not available on most compressors, range sets a maximum amount of attenuation, useful in many gating effects. In the case of ducking, it is likely that the music should be turned down by a specified, fixed amount in the presence of the…. voice. No matter the level of the voice, the music should simply be attenuated by a certain finite amount based on what sounds appropriate to the engineer, perhaps 10-15 dB. [Side-chain] compression would adjust the level of the music constantly based on the level of the voice. The amplitude…. would modulate constantly in complex reaction to the level of the voice. Compression does not hit a hard stop because compressors do not typically process the range parameter. Therefore, look to noise gates for the ducking feature.”

4 To be clear, this is not a criticism of interdisciplinary studies of popular music recording practice. It is, in my opinion, simply a reiteration of Meintjes (2005, 27) observation that “sociology and media studies have led the way in generating discussions about studio-based creativity,” albeit stated here for a very different purpose. A sample of studies which clearly demonstrate this interdisciplinary orientation would have to include: Meintjes (2005); Doyle (2005); Taylor (2001); Sterne (2003); Hennion (1989); Théberge (1997) and Porcello (2005); among many others.

7 See Brackett (1995) for a demonstration of what I mean by “ostentatiously rejecting notation as an analytic tool,” and a great explanation of a now common rationale for doing so. Another helpful article in this respect is Fales’ (2005) “Short-Circuiting Perceptual Systems: Timbre in Ambient and Techno Music.”

8 Again, this is not meant as a criticism but, rather, as a straightforward observation about the goal of these kinds of analyses. Some of the most helpful research on popular music recording practice falls under the heading of “broad procedural chronology,” in my opinion, including: Ryan and Kehew (2008); anything in Richard Buskin’s “Classic Tracks” series in SoundOnSound Magazine as well as Buskin (1991); Martin (1979); Kealy (1979); Millard (1995); and Cunningham (1998); among others.

Théberge, P. (1997) Any Sound You Can Imagine: Making Music/Consuming Technology. Hanover: Wesleyan University Press.

Walser, R. (1995) ‘Rhythm, Rhyme and Rhetoric in the Music of Public Enemy’. In: Ethnomusicology. 39, 1, pp. 193-217.

Zagorski-Thomas, S. (2005). ‘The US vs. The UK Sound’. In: Proceedings of the Art of Record Production Conference. [Online]. 2005. Available at: http://www.artofrecordproduction.com/ (Accessed: November 2009).

Zak, A. (2001) The Poetics of Rock: Making Music/Cutting Tracks. Berkley: University of California Press.